The present invention relates to polyhydroxy compounds containing urea groups and either ester or amide groups, a process for their preparation, and their use.
Carbamoyl lactams, i.e. the adducts of lactams and isocyanates, are known compounds which are of technical interest in polyurethane and polyamide chemistry. The addition products of lactams (in particular of .epsilon.-caprolactam) with polyisocyanates or with isocyanate functional prepolymers of polyisocyanates and polyols, polyamines or polyaminopolyols, are known as masked isocyanates which are unreactive under conditions of storage. They may be formulated with isocyanate reactive compounds (such as polyols) for the preparation of one-component systems which do not harden until the lactam adduct is split up into its components by heating. The lactam can then be detected as volatile product of decomposition while the urethane group is in the product left behind, e.g. ##STR2##
This principle of isocyanate masking is used mainly in the field of lacquers although the temperatures required to release decomposition of the addition product are generally very high (e.g. in the case of .epsilon.-caprolactam, above 160.degree. C.).
Acyl lactams play a role in the chemistry of amino acids and peptides. It is known that acyl lactams open the lactam ring by hydrolysis. The reaction conditions must be very carefully chosen and controlled to ensure that ring opening is not accompanied or replaced by splitting off of the acyl group.
Acyl lactams and carbamoyl lactams play an important role in activated anionic lactam polymerization, where they function as the carriers of chain starting and chain growth. For information on the mechanism of anionic lactam polymerization, see U.S. Pat. No. 3,017,391; and H. K. Reinschuessel, "Lactams", in Kinetics and Mechanisms of Polymerizations, Vol. 2, Ring Opening Polymerizations, publishers K. C. Frisch, pages 303-326, M. Dekker, New York, 1969.
We have now found that the carbamoyl lactam ring can be opened by alcohols under relatively mild conditions if catalytic quantities of strong bases are present according to the following reaction scheme: ##STR3## X.sup.- =base, e.g. alcoholate anion. This reaction proceeds smoothly and with high yields even under relatively mild conditions, e.g. in boiling methanol or ethanol. The side reaction of urethane formation with splitting off of lactam is not found to take place.
If a polyol is used as alcohol component, then new polyhydroxy compounds are obtained, which contain urea groups in addition to the hydroxy and ester group according to the following reaction scheme: ##STR4##
In the above formulae, R represents the hydrocarbon or heterocyclic group of a polyisocyanate having the functionality n and R" represents the group of a polyhydric alcohol having the functionality (a+1).
If the alcohol is replaced by an amino alcohol, the reaction does not result in amino esters but in the corresponding hydroxyamides due to a concomitant or subsequent molecular rearrangement according to the following scheme: ##STR5##